AU2003274632A1 - Highly concentrated aqueous dispersions containing hydrophobic microfine metal oxide particles and a dispersant - Google Patents

Abstract

Aqueous dispersions comprising: A) hydrophobically coated microfine metal oxide particles; and B) at least one of the compounds of the general formula (I) and optionally C) at least one of the compounds of the general formula (II) and optionally D) further auxiliaries and additives, E) water.

Description

IN THE MATTER OF an Australian Application corresponding to PCT Application PCT/EPO3/05204 RWS Group Ltd, of Europa House, Marsham Way, Gerrards Cross, Buckinghamshire, England, hereby solemnly and sincerely declares that, to the best of its knowledge and belief, the following document, prepared by one of its translators competent in the art and conversant with the English and German languages, is a true and correct translation of the PCT Application filed under No. PCT/EP03/05204. Date: 11 November 2004 S. ANTHONY Director For and on behalf of RWS Group Ltd WO 03/103620 e/s/~uujzuzU Highly concentrated aqueous dispersions containing hydrophobic microfine metal oxide particles and a dispersant 5 The invention relates to aqueous dispersions comprising hydrophobic microfine metal oxide particles and, as dispersion auxiliaries, a combination of phosphate esters and maleic anhydride-acrylate copolymers, and to the use of these dispersions for the preparation of cosmetic 10 formulations, in particular sunscreen formulations. To protect the skin against over-intensive UV radiation, cosmetic preparations, such as creams or lotions, containing UV filters are used which are largely 15 transparent and pleasant to use on the skin. As UV filters, they comprise one or more organic compounds which absorb in the wavelength range between 290 and 400 nm: UVB radiation (290 to 320 nm); UVA radiation (320 20 to 400 nm). The higher-energy UVB radiation causes typical sunburn symptoms and is also responsible for suppressing the immune defence, while the UVA radiation, which penetrates 25 more deeply into the layers of skin, causes premature aging of the skin. Since the combined effect of the two types of radiation is said to favor the formation of light-induced skin cancer diseases such as skin cancer, the search for ways of significantly further improving the 30 UV protection already achieved therefore started early on. It has been found that microfine (ultrafine) pigments based on metal oxides can also scatter, reflect and absorb UV radiation. Their high-disperse formulations therefore WO 03/103620 - 2 - UTliEFU/ULZU4 represent an effective addition to organic UV filters in sunscreen compositions. Microfine titanium dioxide is used widely in cosmetic 5 formulations since it is chemically inert and toxicologically safe and leads neither to skin irritations nor to sensitization. It is the currently most used and most important mineral light protection substance. In addition to titanium dioxide, microfine zinc oxide is used 10 to an increasing degree. A distinction is made between coarsely divided material (pigment) and finely divided material (micropigment). For the micropigments, the average primary particle size is 15 usually significantly less than 200 nm, mostly in the range from 10 to 100 nm, usually less than 50 nm. The coarsely divided pigment (0.2 to 0.5 pm) absorbs or reflects broadly and relatively consistently over the 20 entire UV region and the visible light region, while the finely divided material exhibits a significant increase in activity in the UV region with a simultaneous loss of activity in the long-wave UV-A and, in particular in the visible, region. Since only a little visible light is 25 reflected, preparations based on this active ingredient are largely transparent. Due to their particularly large specific surface areas, the microfine TiO 2 particles are photoactive and are able 30 to generate reactive species (e.g. hydroxyl radicals). For use in cosmetic compositions, it is therefore necessary to suppress the photochemical activity. This is achieved by inorganic and organic surface components, such as, for example, A1 2 0 3 , SiO 2 and/or fatty acid (salts), siloxanes.

WO 03/1U36b2U - I - R/teUS/UDZu These substances can adhere to the surface by chemisorption or physisorption (lattice doping/coating). The first leads to grades which are suitable for cosmetic light protection agents. 5 The primary particles of the microfine titanium dioxide are not present in the dry pigment powder in isolated form, but form aggregates and agglomerates. 10 Primary particles refers to the smallest particles which are formed during the preparation of the pigments. Primary particles can be in the form of individual crystallites or else in the form of two or more crystallites which have intergrown tightly with one another along faces. 15 Aggregates refers to particles composed of two or more primary particles, where the primary particles are intergrown with one another along faces. Agglomerate is understood as meaning an association of primary particles or aggregates which are held together via attractive 20 forces, such as, for example, hydrogen bridge bonds. Agglomerates are present in every pigment powder, but are undesired in cosmetic transparent formulations since they can be identified as particles on the skin, often even 25 with the naked eye, reduce the transparency and also the UV protective action of a sunscreen composition and settle out during storage. They therefore have to be largely comminuted again. 30 The entire process of incorporation, comminution and simultaneous distribution of solids in a liquid phase is referred to as dispersion.

WO US/iUJbZU - 4 - '/E/FU/Ub2U 4 As the primary particle size decreases, the specific surface area increases, as does the active area for the formation of aggregates and agglomerates, and also for adsorption processes, as a result of which the stability 5 of emulsions can be endangered. The comminution of the agglomerates and wetting of the newly provided surfaces is only possible with the aid of high shear forces and is carried out in practice in a 10 large number of different special machines, such as, in particular, dissolvers and ball mills. In practice, it has been found that as the finely divided nature of the particles increases, so too do the 15 dispersion problems, with the result that the dispersion process overall represents one of the most complex sub steps in the preparation of cosmetic formulations. The requirements of practice therefore involve separating 20 the most complex part of the dispersion - the comminution of the agglomerates - from the preparation of the actual cosmetic formulations, and preparing stable aqueous dispersions with the highest possible content of microfine TiO 2 which are preferably low-viscosity or at least are 25 still pumpable or flowable. A large number of proposals have been made which aim to solve this problem. 30 GB-A-2 206 339 describes dispersions of titanium dioxide particles of particle size from 0.01 to 0.15 V in organic oils and dispersion auxiliaries based on polyesters, salts of hydroxycarboxylic acids and/or hydroxyl-group-free VYU UJ/±U)Ozu - - UJ/U ZU4

C

6

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22 -fatty acids or salts thereof, and use thereof as sunscreens. Thus, WO-A-90/06103 proposes to reduce the clumping 5 tendency (tendency for reagglomeration of titanium dioxide particles with particle sizes < 100 nm) through coatings made of phospholipids. DE-A-39 41 543 describes a process for the preparation of 10 aqueous dispersions of needle-like finely divided titanium dioxide which is optionally coated with hydrous metal oxides, by grinding the titanium dioxide particles in the presence of a polycarboxylic acid or salt thereof as dispersant, and the use as sunscreens. 15 Although these dispersions have tendential improvements, they still have the disadvantage that the aqueous dispersions comprise insufficiently high contents of microfine TiO 2 , sediment during storage and/or the 20 photoactivity is still too high. A further significant disadvantage is that they are not stable in the pH range from about 5 to 7 (pH of the surface of the skin) which is particularly preferred for 25 cosmetic formulations. The object of the present invention was therefore to overcome the existing disadvantages and to prepare stable high-concentration aqueous dispersions of microfine metal 30 oxide particles, in particular microfine titanium dioxide, with comparatively low viscosities which are also stable in the acidic physiologically favorable pH range.

WU US/IUJbZU - 6 - PCT/EPO3/052U4 The object is achieved through the use of hydrophobically coated microfine metal oxide particles and a combination of phosphate esters and maleic anhydride-acrylate copolymers as dispersion auxiliaries. 5 As well as having a low photocatalytic activity, hydrophobically coated titanium dioxide has a low tendency for reagglomeration since, in particular, the formation of hydrogen bridges via partially present Ti-OH groups of 10 adjacent TiO 2 particles is not possible or is possible only to a low degree. Since hydrophobically coated titanium dioxides are usually not sufficiently water-wettable, aqueous dispersions of these substances are not hitherto known. 15 The invention therefore provides aqueous dispersions comprising A) hydrophobically coated microfine metal oxide particles 20 and, as dispersion auxiliaries, B) at least one of the compounds of the general formula (I) -O-(AO P--OM)b (I) 25 03-b in which R is an optionally branched alkyl radical having 6 30 to 22 carbon atoms which may or may not contain multiple bonds and may or may not contain hydroxyl groups, WU UJ/iUJbZU - / - FCTI/EPUJUbZU4 A is ethylene radical, propylene radical, isopropylene radical, butylene radical, M is H, ammonium ion or an alkali metal cation a is 1 to 30, 5 b is 0 to 2 and optionally C) at least one of the compounds of the general formula (II) 0 k 10 ( I I (lib) COOMa COX (l1b m 0 -k - -mO n _-k in which 15 M is hydrogen, monovalent or divalent metal cation, ammonium ion, organic amine radical a is 1, or where M is a divalent metal cation, is 0.5 X is likewise -OMa or -O-(CpH2pO)q-R 1 where R 1 = H, aliphatic hydrocarbon radical having 1-20 carbon 20 atoms, cycloaliphatic hydrocarbon radical having 5 to 8 carbon atoms, optionally substituted aryl radical having 6 to 14 carbon atoms, p = 2 to 4, q = 0 to 100,

-NHR

2 and/or -NR 2 2 where R 2 = R i or -CO-NH 2 Y is O, NR 2 25 A l is ethylene radical, propylene radical, isopropylene radical, butylene radical, m is 10 to 30, WU UJ/IUJbZU - b - CTI'/EPU.3/UbZU4 n is 0 to 50, k is 10 to 30, where the sum m + k is in the range from 20 to 60, preferably from 20 to 40, 5 optionally D) further auxiliaries and additives E) water. The invention further provides for the use of the aqueous 10 dispersions as claimed in claim 1 for the preparation of the cosmetic formulations. Further subject-matters of the invention are characterized by the claims. 15 The phosphoric esters used according to the invention are ideally represented by the general formula (I) O -o(A P--OM)b (I) L 3-b 20 The nature of the industrial preparation process results in mixtures in which the desired main component, according to the invention preferably the monoester or the diester, are present predominantly alongside small proportions of the further possible reaction products. 25 They are prepared by reacting fatty alcohols R-OH or fatty alcohol alkoxylates R-O-(AO)a-H with phosphoric acid or derivatives thereof by known processes. 30 The co-used fatty alcohols can be prepared by known processes by reducing fatty acids or esters thereof in the presence of catalysts. In the direct hydrogenation, fatty wu ur/±uzu - - eUT/EPOU3/UbZU4 alcohols from triglycerides are reacted with hydrogen in a s'ingle-stage process in a tubular reactor over a Cu/Cr catalyst, giving the reaction products fatty alcohols, 1,2-propanediol and water. In other processes, fatty 5 alcohol from triglycerides is prepared via a transesterification step with subsequent hydrogenation of the fatty acid ester. The fatty acids co-used are, individually or in mixtures, 10 fatty acids, such as caprylic acid, capric acid, 2 ethylhexanoic acid, lauric acid, myristic acid, palmitic acid, palmitoleic acid, isostearic acid, stearic acid, hydroxystearic acid, (ricinoleic acid), dihydroxystearic acid, oleic acid, linoleic acid, petroselic acid, elaidic 15 acid, arachidic acid, behenic and erucic acid, gadoleic acid, and the technical-grade mixtures produced during the pressurized cleavage of natural fats and oils, such as oleic acid, linoleic acid, linolenic acid, and in particular rapeseed oil fatty acid, soybean oil fatty 20 acid, sunflower oil fatty acid, tall oil fatty acid. In principle, all fatty acids with a similar chain distribution are suitable. The content of unsaturated fractions in these fatty acids 25 or fatty acid esters is, where necessary, adjusted to a desired iodine number by the known catalytic hydrogenation processes, or is achieved by mixing completely hydrogenated fatty components with nonhydrogenated fatty components. The iodine number, being a measure of the 30 average degree of saturation of a fatty acid, is the amount of iodine which is taken up by 100 g of the compound to saturate the double bonds.

Vwu ui/uiozu - ±U - PCT/EPU3/Ub204 Preference is given to using the alcohols from partially hydrogenated Cs 8

/

18 -coconut or palm fatty acids, rapeseed oil fatty acids, sunflower oil fatty acids, soybean oil fatty acids and tall oil fatty acids, having iodine numbers in 5 the range from about 80 to 150 and in particular from technical-grade C8/ 18 -coconut fatty acids, where, in some instances, a choice of cis/trans isomers, such as elaidic acid-rich C 16 /1 8 -fatty acid cuts, may be advantageous. They are standard commercial products and are supplied by 10 various companies under their respective trade names. As well as the fatty alcohols, Guerbet alcohols and their alkoxylates, in particular, can also be co-used. 15 The alcohol alkoxylates R-O-(AO)a-H can be obtained by the known processes by the addition reaction of alkylene oxides in the presence of acidic or basic catalysts. The radical -(AO)a- here represents radicals such as ethylene oxide, propylene oxide, butylene oxide and/or 20 tetrahydrofuran, preferably ethylene oxide, where a is an average value of up to 30, preferably 3 to 15 units. In the general formula, -(AO)a- means either a homopolymer of one of said alkylene oxides, or block copolymers or 25 copolymers with random distribution of two or more of the monomers within the polymer molecule. These products are commercially available. They are co used in amounts of from 0.5 to 30%, based on aqueous 30 dispersions, preferably from 3 to 15%, based on aqueous dispersions. In the compounds of the general formula II optionally co used according to the invention WU U/1UJOZU - II - FUCT/EPU3/UbZU4 O k COOMa C-oX- -- (lIla) -M 0 k --m_ O _ k 1. M1 in which 5 M is hydrogen, monovalent or divalent metal cation, ammonium ion, organic amine radical a is 1, or where M is a divalent metal cation, is 0.5 X is likewise -OMa or -0- (CpH2pO)q-R where R = H, aliphatic hydrocarbon radical having 1-20 carbon 10 atoms, cycloaliphatic hydrocarbon radical having 5 to 8 carbon atoms, optionally substituted aryl radical having 6 to 14 carbon atoms, p = 2 to 4, q = 0 to 100,

-NHR

2 and/or -NR 2 2 where R 2 = R i or -CO-NH 2 Y is O, NR 2 15 Al is ethylene radical, propylene radical, isopropylene radical, butylene radical, m is 10 to 30, n is 0 to 50, k 10 to 30, where the sum 20 m + k is in the range from 20 to 60, preferably from 20 to 40, -(AO)a- is either a homopolymer of one of said alkylene oxides, or block copolymers or copolymers with random WU Uj/1Ub2U - 12 - PCT/EPO3/05204 distribution of two or more of the monomers within the polymer molecule, the units 5 [ ]m and [ ]k can likewise be present as block copolymers or copolymers with random distribution of two or more of the monomers within the polymer molecule. The products are co-used in amounts up to 30% by weight, 10 preferably in amounts from 1 to 15% by weight, based on the aqueous dispersions. Microfine metal oxide particles which can be used are in principle all metal oxides customary in the respective 15 fields of use. The term "microfine" or "ultrafine" refers here to primary particle sizes of, on average, < about 250 nm, preferably to about 100 nm and below. For use in cosmetic formulations, the choice is naturally limited to the compounds which are safe from a toxicological and 20 dermatological point of view, such as, preferably cerium oxide, zinc oxide, iron oxide and, in particular, titanium dioxide. The microfine metal oxide particles co-used according to 25 the invention are standard commercial products which are obtainable under the respective trade names, also with inorganic or organic coatings, such as, for example, Micro Titanium Dioxide MT-500B, MT-100 Z and MT-100 TV (all Tri K-Tayca), UV-Titan M 160, M 262, X 161 (all Kemira), 30 Eusolex T-2000 (Merck), Uvinul TiO 2 (BASF), titanium dioxide T-805 and titanium dioxide T-817 (both Degussa). According to the invention, preference is given to titanium dioxide with average primary particle sizes of WU UJ/IUJOZU - L5 - k'/'IVUi/UZZUq < about 250 nm, preferably < 100 nm and in particular in the range from 10 to 100, which are coated with fatty acid (salts) and, in particular, alkylsilanes. 5 Titanium dioxide T 805 (Degussa) has proven particularly advantageous here. Titanium dioxide T 805 consists, in crystallographic terms, of about 80% anatase and about 20% rutile and has a primary particle size of about 21 nm and is coated with trialkoxyoctylsilane. It is characterized 10 by reduced photoactivity, reduced surface activity, high cosmetic acceptance, very good water resistance. In addition to said components, further auxiliaries and additives known in this field can be co-used as desired, 15 such as ethanol, propanol, butanol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, alkoxylates, glycol ethers, glycols, polyethylene glycols, polypropylene glycols, polybutylene glycols, glycerol ester ethoxylates, glycerol, polyglycerol, sorbitol, 20 sucrose, fructose, galactose, mannose, polysorbate, starch, xanthan gum, carrageenan gum, cellulose derivatives, alginates, glycol esters, sorbitan esters, opacifiers, solubilizers, ethoxylated fatty alcohols, sodium chloride, sodium sulfate, magnesium sulfate, buffer 25 systems, cholesterol, pantothenic acid, ascorbic acid, polyacrylic acids, carbomers. The dispersions according to the invention are preferably used for the preparation of cosmetic formulations, such as 30 foundation, colored powders, lipstick, hair colorants, day creams and, in particular, sunscreen preparations, and can be in the customary forms, such as, for example, W/O or O/W dispersions (emulsions), gels, creams, lotions, sprays.

wu U/iUoZU - 14 - PCT/EPO3/05204 The resulting dispersions are characterized by high finely divided nature of the dispersed solid, long-term storage stability, low viscosity and high photostability. 5 The viscosity is measured using a Brookfield RVT, spindle 5, in accordance with the manufacturer's instructions and is, at room temperature at 10 revolutions per minute (rpm), between 10 and 40 000 mPas. 10 The zeta potential can be used as a characteristic of the electrostatic stabilization of a dispersion. The zeta potential is the outwardly effective potential of 15 the particle and represents a measure of the electrostatic interaction between individual particles. It plays a role in the stabilization of suspensions and, in particular, of dispersions with dispersed microfine particles. At a zeta potential value of < -20 mV or > +20 mV, there is strong 20 repulsion between the particles, the dispersions remain stable. At values within this range, the repulsion becomes so low that the van der Waals' forces permit the formation of agglomerates, leading to undesired sedimentation of the particles. 25 The dispersions according to the invention can be prepared by methods generally known in this field, the mixing devices used being automatic dispersers with toothed discs, bead mills, rotor-stator systems, or Scandex 30 shakers. In an expedient manner, the dispersion additives and optionally co-used polyols are introduced into the water, and the pigment is sprinkled in with appropriate stirring.

WO 03/1U362U - 15 - PCT/EP03/05204 The predispersion obtained in this way is then finely dispersed. The aqueous dispersions comprise: 5 5 to 80% by weight of component A), in particular 20 to 60%, 0.5 to 30% by weight of component B), in particular 3 to 15%, 10 0 to 30% by weight of component C), in particular 1 to 15%, 0 to 20% by weight of component D), in particular 1 to 10%, add 100% by weight of water. 15 Auxiliaries and additives which may be co-used are glycerol, propylene glycol, butylene glycol and higher glycol, polyglycerols, sorbitol and comparable sugar alcohols, and 0.1 to 0.5% of water-soluble or water 20 dispersible preservatives.

wU UJ/iUJeiu - b16 - PCT/EP03/05204 Formulation examples: Examples 1 to 4: Example 1 2 3 4 TiO 2 (Degussa T 805) 40.0% 40.0% 40.0% 40.0% Compound of the 7.0% 6.0% 5.0% 8.0% formula II (MW 15 000) Rewophat® EAK 8190 5.0% 6.0% 7.0% Compound of the formula I Guerbet alcohol C12 - - - 6.0% EO-4 phosphate formula I, b = 1 to 2; M = H Glycerol 10.0% 10.0% 10.0% 10.0% Water 38.0% 38.0% 38.0% 36.0% Viscosity (mPas) 340 477 430 1 400 WO US/±UJbZU - 1/ - FUT/EPU3/Ub2U4 Examples 5 to 9: Example 5 6 7 8 UV-Titan M 160"' 40.0% UV-Titan M 262(" - 40% 40% 40% Compound of the 0.5% 11.8% 0.5% formula II (MW 15 000) Guerbet alcohol C18 15.5% 0.5% 11.5% 14% EO-4 phosphate formula I, b = 1 to 2; M = H Glycerol 10.0% 10.0% 10.0% 10% Water 34.0% 37.7% 38.0% 36% Viscosity (mPas) 1 200 600 100 360 ( Commercial product from Kemira, Finland; coated with 5 stearic acid. (2) Commercial product from Kemira, Finland; coated with dimethicone.

WUE U 9:±UiZU - 1- YU'/iU/UbZU' Example 9: Example 9 TiO 2 (Degussa T 805) 40.0% Compound of the 3.0% formula II (MW 15 000) Guerbet alcohol 9.0% C18-4, EO-4 phosphate formula I, b = 1 to 2; M = H Glycerol 10.0% Water 38.0% Viscosity (mPas) 2 800 5 Determination of the zeta potential: The measurements were carried out using the DT-1200 instrument from Dispersion Technology, USA in accordance with the CVI (collodial vibration current) method.

wu U.5/LUI5UzU - ./L-. UJ/U ,ZU4 Zeta potential titration Example No. 4 10 IMr1.2 0.9 10 0.6

,

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0 0,5 -. , '-" -0.842 -15 0.3 -200. -25 0. pH value --- Zeta potential -u-Conductivity Zeta potential titration Example No. 8 101. 1 121 5 -10 0 -15 -M.04 ,20 0.62 0.3 0, -25 0 pH value -*--Zeta potential -- Conductivity ZetapotetialtitrtiI WU US/IUJbzU - zU - ;UT/E UA/UDZUM Zeta potential titration Market product I 10 1.2 5- 1.1 11 0 0. -5 o6 S-15 - D.6 -0.5 N -20 0.4 6 -2 0.3 s0.2 -30 0.1 pH value +-- Zeta potential ---- Conductivity Zeta potential titration Market product II 511 0 1 0 0.9>, -508._ E -100. -15 0.50 o(A -20 0.4 -25 D.3 CL 0. -30 -0.1 -35 0 pH value --- Zeta potential -- Conductivityl WU Ul/iUJbZU - Zi - UT/tLU/U-)ZUq It is clear from the curves that the zeta potential of the dispersions according to the invention is < -20 mV in the entire pH range relevant for cosmetic formulations, and also beyond it, i.e. the dispersions are distinctly 5 stable. By contrast, standard commercial TiO 2 dispersions used for cosmetic formulations have an adequate zeta potential only in a relatively narrow pH range and achieve the 10 isoelectric point in the cosmetically interesting pH range of about 3 to 5.

Claims (8)

1. 3. The aqueous dispersion as claimed in claim 1, characterized in that R is a Guerbet alcohol radical having 6 to 22 carbon atoms, preferably from 12 to 18 carbon atoms, and a is a value between 1 and 30, 5 preferably from 3 to 15.
2. 4. The aqueous dispersion as claimed in claims 1 to 3, characterized in that the dispersion comprises 20 to 60% by weight of microfine metal oxide particles. 10
3. 5. The aqueous dispersion as claimed in claim 4, characterized in that zinc oxide and/or titanium dioxide hydrophobically coated with trialkoxyoctylsilane is co-used as microfine metal 15 oxide particles.
4. 6. The aqueous dispersion as claimed in claims 4 and 5, characterized in that the primary particle sizes of the metal oxides are between 10 and 100 nm. 20
5. 7. The aqueous dispersion as claimed in claims 1 to 6, characterized in that compounds of the general formula II in which A is an ethylene radical, m is 10 to 30, n is 5 to 20, k is 10 to 30 and where the sum m + k is in 25 the range from 20 to 40, are co-used as component C).
6. 8. The aqueous dispersion as claimed in claims 1 to 7, characterized in that compounds of the general formula II in which R is an optionally branched alkyl radical 30 having 8 to 18 carbon atoms which may or may not contain multiple bonds and may or may not contain hydroxyl groups, A is an ethylene radical, M = H or an alkali metal, a is 1 to 30, b is 1 or 2, are co-used as component B). nu uL/±uozu - Zo - PCT/EPO3/05204
7. 9. The aqueous dispersion as claimed in claims 1 to 3, characterized in that the viscosities, measured using a Brookfield RVT, spindle 5, 10 rpm, are between 10 and 5 40 000 mPas.
8. 10. The use of the aqueous dispersions as claimed in claim 1, for the preparation of cosmetic formulations.